17Su11Lec6 - CS17 Neurobiology of Cognition Summer 2011...

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CS17 Neurobiology of Cognition Summer 2011 Lecture 6: Other Perceptual Systems Vestibular System Vestibular Organ , adjacent to Cochlea, consists of two complex structures that provide info for movement, balance Otolith (“Ear stone”) Organs - Detect changes in head tilt relative to body - Hair Cell receptors, embedded in gelatinous substance on which sit Calcium Carbonate crystals - Two chambers (“Vestibular Sacs”): Saculle , lined with Hair Cells on its walls, Utricle with Hair Cells on its floor - Head tilts, gravity makes crystals of Hair Cells => alters NT release Semi-Circular Canals - Detect angular ac/deceleration (e.g from walking, turning) - Three looped canals, each in a different orthogonal (X, X, Z) plane, filled with viscous, potassium-rich (K+) Endolymph - When head begins to rotate, fluid in canal lags behind movement; when head stops, fluid overshoots movement - Hair Cell => alters NT release - In all of the above, deforming Hair Cells results in graded responses to subtle, 3D changes - Bend cilia toward tallest cilia, open K+ gates wide, K+ enters => hypo-polarization, increase Spontaneous firing rate - Bend cilia toward shortest cilia, close K+ gates => hyper-polarization, decrease Spontaneous firing rate - Both informative - Returns to Spontaneous rate when static or at constant velocity - Therefore, Vestibular System only detects change in velocity/orientation PATHWAY : Hair Cells => Vestibular Ganglions , whose axons form tract within 8 th Cranial Nerve (nerve shared w/Audition) => Vestibular Nuclei of Medulla (source of nausea); some directly to Cerebellum (as feedback for acts that require balance ) (Tegmentum) – regulate posture and to Superior Colliculus to coordinate with vision (help determine which movements on retina from head vs. environment) and to Cranial Nerves (3,4,6) that control Eye Movement , to compensate for head (e.g. so can keep focus while head moves) => ?? Temporal Lobe – higher pathway little known
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This note was uploaded on 09/07/2011 for the course COGS 17 taught by Professor Pineda during the Spring '06 term at UCSD.

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17Su11Lec6 - CS17 Neurobiology of Cognition Summer 2011...

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